Powder coating paint can be divided into two main categories; thermoplastic powder and thermoset polymer. Both types of powder coating paint require heat in order to flow and form a uniform film. Each type of paint has its own unique chemical properties and method of application.
Thermoplastic powder is generally applied with a fluidized bed process. No electrostatic charge is required. This type of paint is usually applied to a part that is heated to a temperature well above the powder's melting point. The heat causes the powder to melt, adhere to the part and form a scratch-resistant, uniform film of paint. Unlike thermoset polymers, thermoplastic powders remain chemically unchanged throughout the process, which means that they can be re-melted and reused.
Thermoset powder coating paint differs from thermoplastic powder in that it undergoes a chemical change, called crosslinking, as it cures. After it has been heat cured, this type of finish cannot be re-melted or reused. Thermosetting polymers tend to be more durable than thermoplastics and offer a wider variety of finishes.
There are four categories of thermoset powders that are based on the type of resin used as their base. The four basic resins used for thermoset powders are epoxy, acrylic, polyester and fluoropolymer. In manufacturing thermoset polymers, the resins typically are first ground into a fine powder to make them suitable for spray gun application.
Epoxy-based powder coating is resistant to both impact and scratching. Its inability to stand up to bad weather and ultraviolet rays generally limits its use to indoor applications. Epoxy powder coating paint is generally used for coating home appliances, automotive underbody parts and industrial equipment. It also is a popular choice for painting metal furniture, such as bed frames and futons.
Polyester resins are among the most popular of all types of powder coating paint. They are resistant to ultraviolet (UV) light and perfect for outdoor use. Polyester-based thermoset polymers are often used for coating patio furniture, lawn and garden equipment, car and truck wheels and many other items that are continuously exposed to the elements. These finishes stand up well in harsh weather and offer good corrosion protection.
Acrylic thermosetting powders are most often used in the auto industry. These powders offer a chip-resistant, high-gloss finish that is crystal clear, and these properties make acrylic resins perfect for automotive clear coat paint. Acrylic resins are also used as additives for other powder coating paint materials, such as polyester, to improve flow and leveling and to increase chemical resistance in the final finish.
Fluoropolymer powders offer the highest quality weather-resistant finishes. This type of paint generally is used in architectural applications, such as metal building facades or light poles, and for industrial equipment. Fluoropolymers are also widely employed to coat items that are used in highly corrosive environments, such as marine equipment.